This invention relates to a cutting tool having a resilient clamping mechanism and a replaceable insert retention member.
Cutting tools employing a resilient clamping mechanism for clamping cutting inserts are generally of relatively narrow thickness. For example, cutting operations such as grooving and parting off can be performed by a cutting insert retained in an insert pocket located between the clamping surfaces of upper and lower jaws of a relatively narrow holder blade. The holder blade is, in turn, generally clamped in a blade-retaining block. The holder blade is generally provided with a suitably designed opening, in the vicinity of the insert pocket whereby a relatively narrow bridging portion is formed enabling a limited degree of resilient displacement of one of the holder blade""s jaws relative to the other. Generally, the lower jaw is rigid and the upper jaw is resiliently displaceable. The opening can be of the form of an aperture, or a slot, or a slot terminating in an aperture. Examples of such cutting tools are disclosed in U.S. Pat. No. 3,785,021 and U.S. Pat. No. 4,580,930. A rotary slot-cutting tool employing a resilient insert clamping mechanism is disclosed in U.S. Pat. No. 5,059,068. The cutter body is disc-shaped and of relatively narrow thickness, with cutting insert pockets located around its periphery. As with the holder blade, an insert pocket of a rotary slot-cutting tool has two jaws between which an insert is clamped by means of the resilient force resulting from the bending of the clamping jaw.
Whether the cutting tool is a holder blade or a rotary slot cutting tool, the bending of the clamping jaw is obtained by manufacturing the insert pocket so that the distance between the clamping surfaces of the jaws is smaller than the height of the portion of the insert located between the clamping surfaces. Consequently, when an insert is located in the insert pocket, the clamping jaw is held in a bent position creating an elastic force by means of which the insert is clamped in position.
A well-known problem with cutting tools of the type described above is that the cutting insert is not positively secured in the insert pocket and therefore can become dislodged during cutting operations. For example, this can happen during slotting operations when attempting to withdraw the holder blade from a workpiece. In some cases the cutting insert can be completely pulled out of the holder blade and become embedded in the workpiece. This problem can be especially troubling with rotary slot-cutting tools where the cutting insert can even fly out of the insert pocket under the influence of centrifugal forces. A situation that can be particularly dangerous when operating at high speeds.
It is an object of the present invention to provide a cutting tool with a resilient clamping mechanism in which the above referred to disadvantage is substantially reduced or overcome.
In accordance with the present invention there is provided a cutting tool comprising a body portion and at least one cutting portion, the at least one cutting portion comprising an insert pocket and a cutting insert removably retained therein;
the insert pocket being defined between a clamping jaw and a base jaw, the clamping jaw resiliently connected to the base jaw at a rear portion of the insert pocket; the insert pocket having an insert pocket opening at a front end thereof, the clamping jaw having a first upper side and a first lower side, the first lower side opposing the base jaw and being provided with a forward clamping surface proximate to the front end, the base jaw having a second upper side and a second lower side, the second upper side opposing the clamping jaw and comprising a generally straight first abutment surface proximate the front end connected to a second abutment surface having the form of a circular arc and forming a first recess in the base jaw relative to the first abutment surface;
the cutting insert comprising front and top faces that define a cutting edge at an intersection thereof, and a bottom face located between the front face and a rear face, the top face having a rake surface adjacent the cutting edge and a second abutment surface adjacent the rear face, the bottom face comprises a generally straight third abutment surface adjacent the front face and a fourth abutment surface adjacent the rear face, at least a portion of the fourth abutment surface having the form of a circular segment protruding from the cutting insert relative to the third abutment surface; wherein
the first and second abutment surfaces abut the third and fourth abutment surfaces, respectively, and the clamping surface abuts the second abutment surface.
Preferably, a first aperture is formed between the rear face of the cutting insert and the rear portion of the insert pocket.
Further preferably, a throughgoing second aperture is formed in the base jaw.
In accordance with the present invention, there is also provided a method for inserting and clamping a cutting insert in an insert pocket, the insert pocket being defined between a clamping jaw and a base jaw, the clamping jaw resiliently connected to the base jaw at a rear portion of the insert pocket; the insert pocket having an insert pocket opening at a front end thereof, the clamping jaw having a first upper side and a first lower side, the first lower side opposing the base jaw and being provided with a forward clamping surface proximate to the front end, the base jaw having a second upper side and a second lower side, the second upper side opposing the clamping jaw and comprising a generally straight first abutment surface proximate the front end connected to a second abutment surface having the form of a circular arc and forming a first recess in the base jaw relative to the first abutment surface, the second abutment surface being located on a circle with a given center;
the cutting insert comprising front and top faces that define a cutting edge at an intersection thereof, and a bottom face located between the front face and a rear face, the top face having a rake surface adjacent the cutting edge and a second abutment surface adjacent the rear face, the bottom face comprises a generally straight third abutment surface adjacent the front face and a fourth abutment surface adjacent the rear face, at least a portion of the fourth abutment surface having the form of a circular segment protruding from the cutting insert relative to the third abutment surface;
the method comprising the steps of:
(i) partially inserting the cutting insert in the insert pocket from a side of the insert pocket by placing the fourth abutment of the bottom face of the cutting insert on the second abutment surface of the second upper side of the base jaw on an abutment region so that partial abutment is obtained between the fourth abutment surface and the second abutment surface, with the top face of the cutting insert located outside the insert pocket;
(ii) rotating the cutting insert about the abutment region into the insert pocket until the top face of the cutting insert is located inside the insert pocket, and the second abutment surface of the top face of the cutting insert is situated opposite the first lower side of the clamping jaw with the clamping surface of the first lower side of the clamping jaw located opposite the rear portion of the rake surface;
(iii) rotating the cutting insert in the insert pocket about the center of the circle on which the second abutment surface is located until the cutting insert is clamped in position with the third abutment surface of the bottom face of the cutting insert abutting the first abutment surface of the second upper side of the base jaw, the central portion of the fourth abutment surface of the bottom face of the cutting insert abutting the second abutment surface of the second upper side of the base jaw and the clamping surface of the first lower side of the clamping jaw abutting the second abutment surface of the top face of the cutting insert.